Communicating system



IP8102 OR 291659062 July 4, 1939. J. R. M KAY 2,165,062

X1 I COMMUNICATING SYSTEM ,1 Original Filed June 11, 1934 M 1 v f a INVENTOR L. J ta lmfifiarfi'aq I m, 9624 MM ATTORNEYS Swmh Hwy;

Patented July 4, 1939 UNITED STATES PATENT OFFICE COMMUNICATING SYSTEM John R. MacKay, West Caldwell, N. .L, assignor to Wallace & Tiernan Products, Inc., Belleville, N. J., a corporation of New Jersey 9 Claims.

This invention relates to communicating systems. More particularly it relates to telephone systems and from a still more specific aspect it relates to radio telephone systems. cation is a division of my copending application, Serial No. 730,127, filed June 11, 1934, for Communicating systems, which has issued as Patent No. 2,115,914 on May 3, 1938.

One of the objects of the invention is to provide a two-way radio telephone system in which the user at the calling station operates a call switch and the user at the called station receives a signal, as the ringing of a bell, thereupon lifts his telephone receiver from its hook, and thereby the user at the calling station is given a signal, as by means of a bell, indicating that his call has been put through, and the user at the calling station thereupon removes his telephone receiver from its hook, and two-way telephone connations thereof whereby the communication system is comparatively inexpensive to build and operate, comparatively simple in operation from the standpoint of the intelligence required to use it, and thoroughly reliable in its operation. Other objects and advantages will appear as a preferred form of the invention is hereinafter disclosed.

The drawing illustrates an embodiment of what is considered to be a preferred form of the invention, and shows a wiring diagram of the apparatus at one of two stations between which radio telephone communication is to be established and maintained. The wiring diagram of the apparatus at the other station in the system may be, and by way of example is here assumed to'be, identical with that shown in the drawing. For convenience, therefore, the two stations will be identified as station A and station B,- and in the following description the drawing will be taken to represent each of the stations in turn, as will be explained. It will be understood, however, that the transmittingapparatus at station A is adapted or adjusted to emit a high frequency carrier wave at a frequency difierent from This appli-' (Cir 0,

that of the high frequency carrier which the transmitting apparatus at station E is adapted or adjusted to emit, and that the radio receiving apparatus at station A is tuned to the carrier frequency of station B, and the radio receiving apparatus at station B is correspondingly tuned to the carrier frequency of station A. Each station of the system includes radio reeiving apparatus and radio transmitting apparatus. The receiving apparatus is adapted to receive radio telephone signals and convert them to sound frequency speech-representing currents, and the transmitting apparatus is adapted to have its filament and plate supply rendered operative upon energization of the transmitter control relay 2| so as to emit a desired carrier frequency and also properly to modulate it when telephone conversation takes place in the manner later to be described.

The radio transmitting apparatus shown in the drawing is designated generally as I enclosed in the dot and dash lines. Although other suitable forms of radio transmitting apparatus may be employed, the apparatus illustrated comprises an oscillator designated generally as IM and which comprises a push-pull oscillator of well known construction and operation, which feeds into two antennas I02 and I03 which are each tuned to one-quarter wave-length. The transmitting apparatus comprises also a suitable modulator I04 of standard construction and adapted to superimpose the voice modulated currents upon the high frequency oscillations generated by the oscillator NH and supplied to the antennas I02 and I03. With this description it is believed that the construction of the radiotransmitting apparatus will be quite clear to those skilled in the art. The various tuning instrumentalities, coupling coils, and plate current supply sources, etc. will be readily recognized by their usual symbols and from the diagrammatic illustration; it being understood, of course, that other forms of apparatus may be employed such as suitable plate circuit power supply instead of the plate battery supply shown in the wiring diagram.

The radio receiving apparatus or set shown at I05 is a so-called super-regenerative receiving set. It comprises a vacuum tube system I06 so tuned and connected as to generate high frequency oscillations by regeneration or feedback. The operation of the oscillator I06 will be understood by those skilled in the art upon inspection of the wiring diagram; suflice it to say that the tuning condenser I01 gives a large frequency earth range but comparatively sharp tuning whereas the tuning condenser I 08 has a limited frequency range and permits of a vernier action, so to speak, so as to facilitate tuning that would be rendered much more difficult if the sharply tuned condenser I'I were present alone. It will be understood, of course, that the ordinary users of the apparatus do not do any of this tuning but it is a matter of initial adjustment, and which remains fixed after satisfactory initial adjustment. It will be further understood by those skilled in the art that the tube I06 with its circuits serves not only as a generator of high frequency oscillations but also as a detector tube as in the ordinary super-regenerative operation.

The radio receiving apparatus I comprises also a low frequency oscillator I09 which is so connected and coupled as to generate the socalled quenching frequency for the: system of the tube I06. The quenching system comprising the tube I09 is connected to the oscillator system, comprising the tube I06, by a conductor H0 in which are connected in series a suitable condenser III and a radio frequency choke coil H2. The condenser III passes the desired quenching frequency and the choke coil II2 prevents the passage from the tube system I06 to the remainder of the radio receiving system, of high frequency oscillations generated in the tube system I06. A transformer I I3 having its primary shown shunted across the condenser II I transfers the audio components of the system I06-I09 to the grid circuit of an amplifying vacuum tube II4; the secondary of the trans-, former I I3 being connected in the grid circuit of the tube H4. The plate of the vacuum tube H4 is connected to the conductor 20 of the control apparatus.

As in the case of the illustration of the radio transmitting apparatus, the radio receiving apparatus may be supplied from a suitable plate current source such as the well known B battery illustrated, or any other suitable plate supply.

The operation of the super-regenerative receiving apparatus is so familiar to those skilled in the art that the diagram and foregoing description, supplemented by the description of operation hereinafter set forth, will enable its construction and operation to be fully and clearly understood.

Each station includes an intermittently operating or cycling mechanism having for its principal purposes the conservation of apparatus and of energy required.

A motor 33 is provided for continuously rotating a cam 34 which periodically operates the cam switch 35. While this motor may assume a variety of different forms, I prefer at present to employ a motor of the magnetic type, such as that described and claimed in United States Patent No. 1,985,357 for Electric motor apparatus, granted December 25, 1934, upon the application of Charles F. Wallace.

The normal circuit of the motor (during intervals when contacts 36 of the cam switch 35 are not opened by cam 34) is as follows: from the positive side of the 7 volt battery through the winding of the motor 33, through contacts 36 (now closed), back to the negative side of the 7 volt battery. The motor 33 normally continues to run, and together with its cam switch and other instrumentalities, including the relay 24, operated in the manner hereinafter described, automatically and intermittently causes the vacuum tubes of the receiving apparatus I05, and the transfer or control vacuum tube 26,

to be supplied with energy. By this means the consumption of energy is minimized and the life of the apparatus prolonged.

In the system shown, the cam 34 which is operated by the motor 33 has a medium spot as well as a high spot so that upon rotation of the cam in a counterclockwise direction by the motor 33, the medium spot of the cam first causes the contacts 38 to close while the contacts 42 are still open; and continued rotation of the cam in its counterclockwise movement causes the high spot of the cam to close the contacts 42. By virtue of this construction of the cam and the contacts operated thereby the contacts 38 close sufiiciently in advance of closure of the contacts 42 as to permit the relay 21 to be energized by closure of the contacts of the relay 40, so as to open the circuit of the bell 28 at the contacts 32 before the contacts 42 of the cam switch close the bell circuit. In other words, time is afforded for the filaments of the vacuum tubes of the receiving apparatus and the filament of the tube 26 to become sufficiently heated so as to place the receiving apparatus in condition for operation hereinafter referred to so as to prevent inadvertent or undesired operation of the bell 28. It will be understood that the bell 28, or other signaling device, is provided at each station to advise the attendant when he is wanted on the telephone, i. e., when a carrier is received from the other station.

The grid circuit of the transfer or control vacuum tube 26 at each station is preferably provided with a filter comprising a suitable condenser I5 shunted across the secondary of the transformer 5| and with a suitable choke coil I6 in series with the grid so as to permit the desired audio frequency components of the rush cur rent to be impressed upon the grid but to suppress undesired frequencies above the audible rush range. What is meant by rush current will be hereinafter explained.

The operation of the system illustrated will be understood in view of the foregoing explanations, supplemented by the following.

Assume that no signal is being received by the antenna I20 of the radio receiving apparatus I05. The motor 33 is rotating its cam 34 continuously. When the medium spot of the cam operates the cam switch 35 to close the contacts 38, the relay 24' is energized in the following circuit: from the positive side of the 7 /2 volt battery, through the relay 24, through the contacts 38, back to the negative side of the 7 volt battery. Energization of the relay 24 causes the filaments of all of the vacuum tubes of the radio receiving apparatus I05, and also the filament of the vacuum tube 26, to be energized. Under the assumption made, i. c. with no signal being received by the antenna I20, the rush current in the output of the super-regenerative receiving apparatus is transmitted through the transfer circuit and tube 26 and energizes the relay 40 to cause the latter to close its contacts. Energization of the relay 40 closes the following circuit: from the positive side of the 7 volt battery, through the contacts of the relay 40, through the contacts 4| of the hook switch 30, through the relay 21 and back to the negative side of the 7% volt battery. Energization of the relay 21 causes its contacts 31' to close and in view of the fact that these contacts 31' are in parallel with the now open contacts 36 of the cam switch 35, the motor circuit is maintained, even if it has been opened at 36, and the motor continues to run.

Energization of the relay 2'! causes the contacts 32' to open before the contacts 42 of the cam switch 35 have become closed by the high spot of the cam. Therefore, the circuit of the bell 28 is opened at the contacts 32' before the bell circuit is closed at the contacts 42, and the bell 28 therefore does not ring when the high spot of the cam causes the contacts 42 subsequently to close.

The motor 33 continues to rotate the cam 34 and the cam switch 35 opens its contacts 38 and 42 and closes its contacts 36 so that the parts are restored to their positions indicated in the draw- By this periodic operation just described, the radio receiving apparatus and the tube 26 are rendered operative or receptive periodically.

The construction and connections may be satisfacto-rily explained by describing the operation of the system assuming that the user at station A desires to call the user at station E and thereafter converse with him as in customary use of two land line telephones connected for that purpose. Although it is thus here assumed that station A is the calling station and that station B is the called station, it will be understood that either station may be the calling or called station.

Le it be further assumed, for the moment, that the station shown in the drawing represents station A, i. e. the station from which it is desired to make a call. The user at the calling station A throws his call switch 22 to the calling position. This operation of the call switch 22 to the calling position establishes the following circuit: from the positive side of the 7 volt battery, through the transmitter control relay 2 I, through the now closed contacts 23 of the call switch, back tothe negative side of the 7 volt battery. Energization of the transmitter control relay 2| causes energization of all of the filaments of the vacuum tubes of the radio transmitting apparatus I00 and causes the plate batteries to supply plate current to the various tubes. The radio transmitting apparatus now begins to emit and continues to emit a carrier wave of high frequency from the calling station A.

Operation of the call'switch 22 to the calling position also closes the following circuit through the relay 24: from the positive side of the 7% volt battery, through the relay 24, through the contacts 25 of the call switch 22, back to the negative side of the 7%; volt battery. Energization of the relay 24 causes the vacuum tubes of the radio receiving apparatus at the calling station A to be supplied with filament and plate current and likewise causes the vacuum tube 26 to be supplied with filament and plate current. This places the radio receiving apparatus at the calling station A in receptive condition for the answer back call and for subsequent speech communication.

Operation of the call switch 22 to calling position also places the following signal circuit in condition to be energized if and when the relay 2'! becomes deenergized in the manner later to be described: from the positive side of the 7% volt battery, through the bell or signaling device 28, through the contacts 29 of the hook switch 30, through the contacts 3I of the call switch 22, through the contacts 32 (now open because the rush current of the now activated radio receiving apparatus has energized the relay 43 and consequently caused energization of the relay 27), back to the negative side of the 7 volt battery.

By the operation of the call switch 22 to its team com calling position the radio transmitting apparatus at the calling station A has been put into operation to cause a high frequency carrier wave to be emitted; the radio receiving apparatus at the calling station A has been placed into operative receptive condition; and the circuit of the bell 28 at the calling station has been placed in condition to advise the user at the calling station upon the receipt of an answer back in the manner later to be described.

The high frequency carrier wave transmitted from station A, as above described, is intercepted by the antenna I20 of the called station B (the drawing now being assumed to represent the apparatus at station E, i. e. the called station). The antenna or collector I20 and its associated input circuit of the radio receiving apparatus at station B has been tuned, as by means of the variable condensers I2 I, I01, I08, to the frequency of the carrier transmitted from the calling station A. The super-regenerative receiving apparatus which generates and supplies rush current through the tube system 26 to the relay 40 (when the filament and plate circuits of its tubes are established and no carrier is being received) so as to maintain the relay 4!] energized, now has its rush current suppressed or reduced by the received carrier so as to cause the relay 4!] to become deenergized. This. deenergization of the relay 40 continues so that the contacts of the relay 40 are opened and remain open.

It will be understood that the super-regenerative receiver at the called station E is not continuously in receptive condition since its filament and plate supplies are established only periodically by the operation of the motor operated cam switch 35 at that station. When the medium spot of the cam closes the contacts 38 of the cam switch 35, the relay 24 at the called station B is energized and thereby the filament and plate supplies to the radio receiving apparatus and the tube system 26 at the called station B become operative. It is during this period of operative-' ness of the receiving apparatus at the called station B that the rush current is reduced by the received carrier frequency, as stated above, to produce deenergization of the relay 40. With the relay 4!] deenergized., its contacts remain open so that the relay 2'! does not become energized. Now as the high spot of the cam 34 at the called station E closes the contacts 42, the circuit of the bell 28 is established at the contacts 42, and since the contacts 32' in the bell circuit are now closed, the bell 28 at the called station B begins to ring and continues to ring. When the circuit of the motor 33 is interrupted by the opening of the cam switch contacts 36 at the called station the shunting contacts 3'! of the relay 2'! are now open so that the motor stops. The user at the called station B, hearing his bell 28, now removes his telephone receiver or head piece 53 from the hook of the hook switch 3!) thereby 'automatically causing the contacts 29 and M of the hook switch 30 at the called station B to open and the contacts 43 of the same hook switch to close.

Opening of the contacts 29 of the hook switch 30 at station B opens. the circuit of the bell 28 and the latter ceases to ring.

Opening of the contacts M of the hook switch 30 at station E opens the circuit of the relay 21, which circuit is also open at the contacts of the relay 40.

It is desirable to maintain the relay 2'I deenergized so as to prevent rotation of the motor 33 during transmission of speech, and therefore it is necessary to open the motor circuit, by opening the circuit of the relay 21 at the contacts 4| of the hook switch 30, lest subsequent speech modulation causes spasmodic operation of the relay 2! with the particular input circuit shown.

Closure of the contacts 43 of the hook switch 30 at station B causes the relay 45 to be energized through the following circuit: from the positive side of the 7 volt battery, through the contacts 43 of the hook switch 30, through the relay 45, back to the negative side of the 7 volt battery. Energization of the relay 45 causes its four sets of contacts to close.

Closure of the contacts 46 of the relay 45 completes the following circuit for the relay 24: from the positive side of the 7 volt battery, through the relay 24, through the contacts 45 of the relay 45, back to the negative side of the 7 volt battery. This circuit maintains the radio receiver at station B in operative condition.

Closure of the contacts 47 of the relay 45 establishes the following circuit for the relay 55: from the positive side of the 7 volt battery, through the contacts 41 of the relay 45, through the relay 50, back to the negative side of the 7 volt battery. Energization of the relay 50 disconnects the plate or B battery supply from the primary of the input transformer 5| of the tube 26, and connects the plate or B battery supply to the primary of the transformer 52 which is connected at its other side to the plate of the tube 4 of the receiving apparatus I05 at station B. The secondary winding of the transformer 52, it will be noted, is connected to the telephone receiver or head piece 53.

Closure of the contacts 48 of the relay 45 connects the microphone or transmitter 54 in series with the microphone battery and the microphone input to the radio transmitter at station B.

Closure of the contacts 49 of the relay 45 establishes the following circuit through the transmitter control relay 2|: from the positive side of the 7 /2 volt battery through the transmitter control relay 2|, through the contacts 49 of the relay 45, back to the negative side of the 7 /2 volt battery. Energization of this transmitter control relay 2| causes the filament and plate supplies of the radio transmitter at station B to become operative and to transmit a high frequency carrier wave at a frequency different from that emitted at station A and to which the receiver at station A is tuned.

Except that the frequency of the carrier emitted at station A is diiferent from that emitted at station B and except for the fact that the radio, receiving apparatus at station A is tuned to the carrier of station B, and the radio receiving apparatus at station B is tuned to the carrier frequency at station A, the apparatus and connections at sations A and B are identical.

Returning now to the calling station, i. e. station A, and assuming that the drawing represents station A, the carrier wave transmitted from the called station (station B) is received at station A, and, by driving down the rush current, causes the relay 40 at station A to be deenergized. Deenergization of the relay 40 causes its contacts to open to deenergize the relay 21. Deenergization of the relay 21 causes the contacts 32' to close and thereby closes the circuit of the bell 28 at station A. The bell 28 therefore rings at station A and thus advises the user at station A that his call upon station B has been put through.

The user or attendant at station A now removes the telephone receiver or head piece 53 from its hook, which automatically causes the contacts 29 and 4| of the hook switch 30 to open and the contacts 43 thereof to close.

The circuit of the bell 28 is thereupon opened at the contacts 29 and the bell ceases to ring.

Removal of the receiver 53 from its hook at station A also opens the circuit of the relay 2'! at the contacts 4| of the hook switch 3|].

Closure of the contacts 43 of the hook switch 30 establishes the following circuit through the relay 45: from the positive side of the 7 /2 volt battery, through the contacts 43 of the hook switch 30, through the relay 45, back to the negative side of the 7 volt battery.

This energization of the relay 45 closes the four pairs of contacts of that relay.

Closure of the contacts 46 of the relay 45, which contacts are in parallel with the contacts 25 of the call switch 22, insures that the relay 24 shall be kept energized until conversation has ceased and even though the call switch 22 may have been returned to its 01f position.

Closure of the contacts 49 of the relay 45, which contacts are in parallel with the contacts 23 of the call switch 22, insures that the transmitter control relay 2| shall be kept energized until conversation has ceased and even though the call switch 22 may have been returned to off position.

Closure of the contacts 41 of the relay 45 connects the relay 50 across the 7 volt battery. Energization of the relay 50 disconnects the plate or B battery supply from the primary of the input transformer 5| of the tube 26, and connects the plate or B battery supply to the primary of the transformer 52 which is connected at its other end to the plate of the tube I H of the radio receiving apparatus at this station (A) under consideration. The secondary winding of the transformer 52, it will be noted, is connected to the telephone receiver or head piece 53.

Closure of the contacts 48 of the relay 45 connects the microphone 54 to the microphone battery and to the microphone input of the radio transmitter.

Telephone conversation may now be carried on between stations A and B as in the case of persons conversing over ordinary land line telephones which have been properly connected, i. e. each person may interrupt the other and in all respects converse in the usual manner.

When conversation has ceased, the users at stations A and B merely hang up their receivers or head pieces 53 on the hooks of the hook switches 30 and the user at station A throws his call switch 22 to the off position (if the last mentioned switch has not already been moved to the 01f position) and the parts are all automatically restored to their normal positions.

Recapitulating: When the operator at either station desires to call the other station, all that he does is to throw his call switch to calling position. This automatically causes the bell to ring at the called station and when the attendant at the called station removes his telephone receiver from its hook the bell rings at the calling station, the user at the calling station then removes his receiver from its hook and two-way conversation then proceeds. After conversation has ceased each user at his station hangs up his receiver on its hook and the user at the calling station throws his calling switch to the off position.

While not essential. I prefer to provide a pilot light at each station to indicate when the call switch at that station has been operated to its calling position and to indicate the operation of the motor 33 at that station; the circuit and op-- eration of the pilot light being as described in my copending application Serial No. 730,127, now

- Patent No. 2,115,914 issued May 3, 1938. By-pass condensers BI, 62 and 64, rheostat 65 and volume control potentiometer 66 are provided as in the case of the system shown in Figs. 1a and 1b of my said copending application. Likewise a condenser 61 and resistance 68 are shown connected across the contacts 42 to provide a means for suppressing sparking or arcing at these contacts.

In the preceding description of the apparatus illustrated, reference was made to employment of the rush current characteristic of superregenerative receiving apparatus for operating the relay 40. I shall now proceed to explain what I believe to be the theory of operation which produces this rush current effect.

This rush is partly due to the irregular production of beats between the quenching frequency oscillator and the detector and to the tremendous sensitivity of the super-regenerative receiver. The beats between the detector and the quenching or interruption frequency oscillator Vary so rapidly and so irregularly that a resultant beat frequency component or rush is produced. In addition, tube noises usually of low audibility in ordinary receivers are amplified to such an extent as to become plainly audible. When an incoming carrier is impressed on the detector it serves to block the peaks at which the detector oscillates, providing it is of suflicient strength, and thus suppresses or reduces most of the socalled rush.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use within the scope of the appended claims.

I claim:

1. In a wave signalling system, in combination, a super-regenerative receiving circuit, a relay, and means responsive to the rush current in the output of said circuit normally energizing said relay, said circuit including means for causing said relay to become deenergized upon reception of a rush-depressing carrier.

2. In a station of a wave signalling system, in combination, super-regenerative wave receiving means having an output circuit and including means for setting up a rush current in said circuit when waves are not received and means for suppressing said rush current on receipt of Waves, a signalling device, an energizing circuit therefor,

and means controlled by the output circuit of the receiving means and responsive to absence of rush current in said output circuit for closing the energizing circuit of the signalling device whereby the latter is operated to indicate reception of waves at the station.

3. In a station of a wave signalling system, in

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combination, a super-regenerative receiving circuit, means for periodically supplying local energy to said circuit, a signalling device, an energizing circuit therefor, means controlled by the super-regenerative circuit and responsive to absence of rush current therein for closing the energizing circuit of the signalling device when the rush current is depressed by a received carrier, and contact means associated with the periodic energy-supplying means for maintaining the energizing circuit of the signalling device in open condition during a preliminary interval of energy supply to the super-regenerative circuit, to prevent false operation of the signalling device during such interval.

4. A radio wave receiving system comprising a super-regenerative receiving apparatus having an output circuit and normally adapted, when energized, to set up a rush-current in said output circuit unless a rush-depressing carrier is received, and means including a signalling circuit and relay apparatus responsive to the rush-current in the aforesaid output circuit and adapted to control the signalling circuit, for indicating absence of the rush-current.

5. The radio wave receiving system described in claim 4, which includes means including a source of energy for initiating energization of the receiving apparatus, and means for maintaining the indicating means out of rush-depression responsive condition during a preliminary interval of energy supply to the receiving apparatus under control of the energization-initiating means, to prevent untimely indication of the absence of r sh-current.

$26. A radio wave receiving system comprising 1 a calling device, radio wave receiving apparatus having an output circuit and having means which include a source of oscillations and which are operable during times when incoming waves are not received, and only in response to energized operation of the receiving apparatus when the latter is in proper condition for wave reception, for setting up a characteristic energization in said output circuit in response to oscillations from said source, means controllable by said output circuit for operating the calling device upon absence of the aforesaid characteristic energization in said output circuit, means for intermittently supplying energy to the receiving apparatus to render the latter operative during the intervals of energy supply, and associated means for rendering the calling device operating means ineffective to initiate operation of the calling device during the intervals when the aforesaid intermittent means does not effect its said energy supply.

'7. A radio wave receiving system comprising a calling device, radio wave receiving apparatus having an output circuit and having means which include a source of oscillations and which are operable during times when incoming waves are not received, and only in response to energized operation of the receiving apparatus when the latter is in proper condition for Wave reception, for setting up a characteristic energization in said output circuit in response to oscillations of the calling device at other intervals, and means associated with the aforesaid calling device operating means, and. controllable therewith when the calling device is operated, for rendering said intermittent operating means ineffective to prevent operation of the calling device, and for thereby maintaining the calling device in operation.

8. A radio wave receiving system commising a calling device, radio wave receiving apparatus having ai'f" output circuit and having means which include a source of oscillatignsyand which are operable during times when incoming waves are not received, and only in respqnsentoncnersized operation of efl neceivine appa atusmhen the latter is in proper condition forwave. recep tion, for setting up a characteristic energization in said output circuit in response to oscillations from said source, intermittent control means igr causing said receiving apparatus to:operate to set up said characteristic energization at intermittent intervals, and means controllable by said output circuit and in response to absence of said energization therein during said intervals, for operating the calling device,said intermittent control means including meansufor pre vqr lt n operation of said calling device.ioperating.means during other than said intervals, and said calling device operating means including means brought into play when the calling devi is operated, for then preventing said intermittent. control means from et fif l neration tith callin device.

9. A radio wave receiving system comprising a super-regenerative receiving apparatus, a relay and means responsive to the rush-current in the output of said apparatus for energizing said relay when the apparatus is in operative condition, and an electrical circuit controlled by the relay and in response to deenergization of said relay upon absence of the rush-current.

JOHN R. MACKAY. 

